Evidence suggests that the prevalence of attention-deficit hyperactivity disorder (ADHD)/hyperkinetic disorder (HKD) is greater in males than females.1,2

The large European ADORE (Attention-Deficit Hyperactivity Disorder Observational Research in Europe) study was a 24-month naturalistic longitudinal observational study in 10 European countries of children (aged 6–18 years). In total, 1478 patients were analysed: 231 girls (15.7%) and 1222 boys (84.3%) [Gender data are missing for n=25].

Gender ratios varied by country ranging from 1:3 to 1:16 in females:males (Figure).1

Male:female ratios in child and adolescent ADHD (n=1478) by European country. Reproduced with kind permission.1

ADHD is more commonly diagnosed in adult males compared with adult females. A worldwide meta-regression analysis of 11 studies of adults with ADHD found that although the ratio of males to females with ADHD decreased with age, a gender difference was still present in adults aged 19 years and over (Figure).2

Male:female ratio in adults with ADHD from a worldwide meta-regression analysis (n=14,081)2

However, in a 7-year matched case-control study of 219 adults with ADHD and 215 adults without ADHD, interaction analyses found that gender did not moderate the association between ADHD and phenotypic presentation of the disorder. In fact, the number of ADHD symptoms, and the distribution of symptom clusters of inattention, impulsivity and hyperactivity, was found to be highly similar between genders.3

Researchers in this study concluded that the similar pattern of psychiatric disorders and impaired psychosocial/school functioning between males and females with ADHD indicate that aetiologic factors for ADHD may not differentiate between gender, and that both males and females with ADHD are severely under-identified and under-treated.3

Symptoms of ADHD may differ between genders

Some studies have indicated that girls with ADHD may be up to twice as likely as boys to have the inattentive type of ADHD and may suffer more from internalising symptoms and inattention, in contrast with the hyperactive and aggressive symptoms shown by boys.4-6 Differences in ADHD presentation between boys and girls may explain the lower prevalence rates of ADHD in females.

However, the large European ADORE study of clinically referred children (n=1478; mean age: girls=8.8 years, boys=9.0 years) found no evidence to suggest that core ADHD symptomatology differed between genders.1

Research in adults with ADHD has indicated that both genders have similar phenotypic features following adolescence.3

ADHD persistence from childhood to adulthood is similar between genders

ADHD persists from childhood to adulthood in ~50–66% of individuals.7-9 Two studies (one in males, one in females), which examined the persistence of ADHD in patients who had received an initial diagnosis when aged 6–17 years, reported that 11 years after the initial diagnosis, 35% of males and 33.3% of females continued to meet Diagnostic and Statistical Manual of Mental Disorders – 4thedition (DSM-IV)* criteria for ADHD; indicating that persistence is similar between genders.10,11

Despite the apparent gender differences, research has mainly focused on ADHD in males; the pool of research into ADHD in females is slowly increasing, yet is still limited.11

*These studies were conducted prior to publication of the Diagnostic and Statistical Manual of Mental Disorders – 5th Edition (DSM-5TM).